Extended articulation orthopaedic implant

ABSTRACT

A kit for use in performing joint arthroplasty, the kit including a prosthesis to be fitted to a long bone and a cutting guide. The cutting guide including a housing having an attachment mechanism adapted to couple the housing to the bone during arthroplasty and a wall defining a continuous path and a blade for cutting the bone, the blade fitting within and sliding along the continuous path such that the blade cuts the bone in a shape matching the second body articulating surface.

This application is a divisional of co-pending application Ser. No.12/609,028, which is a continuation in part of U.S. Pat. No. 7,517,364filed on Mar. 31, 2003. The disclosure of both are hereby incorporatedby reference in their entireties.

Cross reference is made to the following applications: DEP755USNPentitled “ARTHROPLASTY SIZING GAGE”, U.S. Pat. No. 7,527,631,DEP0755USDIV1 entitled “Joint Arthroplasty Kit and Method”, U.S.application Ser. No. 12/410,032, DEP756USNP entitled “ARTICULATINGSURFACE REPLACEMENT PROSTHESIS”, U.S. application Ser. No. 10/403,750now abandoned, DEP0756USDIV1 entitled “ARTICULATING SURFACE REPLACEMENTPROSTHESIS”, U.S. application Ser. No. 12/429,662, now abandoned,DEP0789USNP entitled “MODULAR ARTICULATING SURFACE REPLACEMENTPROSTHESIS”, U.S. application Ser. No. 10/403,577 now abandoned,DEP5041USNP entitled “ARTHROPLASTY INSTRUMENT AND ASSOCIATED METHOD”,U.S. application Ser. No. 10/403,710 which has issued as U.S. Pat. No.8,366,713, DEP5042USDIV1 entitled “Bone Preparation Tool Kit andAssociated Method”, U.S. application Ser. No. 12/421,335 which hasissued as U.S. Pat. No. 8,444,646, DEP5042USCNT1 entitled “ExtendedArticulation Orthopaedic Implant”, U.S. application Ser. No. 12/421,308which has issued as U.S. Pat. No. 8,182,541 and DEP5052USNP entitled“PROSTHETIC IMPLANT, TRIAL AND ASSOCIATED METHOD”, U.S. Pat. No.7,338,498, DEP5052USCIP1 entitled “Punch, Implant and AssociatedMethod”, U.S. application Ser. No. 10/794,628 which has issued as U.S.Pat. No. 8,105,327 and DEP5052USCNT1 entitled “Prosthetic Implant, Trialand Associated Method”, U.S. application Ser. No. 11/900,682, nowabandoned, which are incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to the field of orthopaedics,and more particularly, to an implant for use in arthroplasty.

BACKGROUND OF THE INVENTION

The present disclosure relates generally to prosthetic joints, and moreparticularly to a shoulder implant system.

The invention relates to implantable articles and methods for implantingsuch articles. More particularly, the invention relates to a boneprosthesis and a method for implanting the same.

There are known to exist many designs for and methods of implantingimplantable articles, such as bone prostheses. Such bone prosthesesinclude components of artificial joints, such as elbows, hips, knees andshoulders.

Early designs of implantable articles relied upon the use of cements toanchor the implant. However, the current trend is to use cements to alesser extent because of their tendency to lose adhesive properties overtime and the possibility that cement contributes to wear debris within ajoint.

Recently, implantable bone prostheses have been designed such that theyencourage the growth of hard bone tissue around the implant. Suchimplants are often implanted without cement and the bone grows aroundsurface irregularities, for example, porous structures on the implant.

One such implantable prosthesis is a shoulder prosthesis. During thelifetime of a patient it may be necessary to perform a total shoulderreplacement procedure on a patient as a result of, for example, diseaseor trauma, for example, disease from osteoarthritis or rheumatoidarthritis. Currently, most implantable shoulder prostheses are totalshoulder prostheses. In a total shoulder replacement procedure, ahumeral component having a head portion is utilized to replace thenatural head portion of the upper arm bone or humerus. The humeralcomponent typically has an elongated intramedullary stem, which isutilized to secure the humeral component to the patient's humerus. Insuch a total shoulder replacement procedure, the natural glenoid surfaceof the scapula is resurfaced or otherwise replaced with a glenoidcomponent that provides a bearing surface for the head portion of thehumeral component.

With the average age of patients requiring shoulder arthroplastydecreasing, device manufacturers are developing bone sparing implantsfor the initial treatment of degenerative arthritis. Surface replacementprostheses are being developed to replace the articulating surface ofthe proximal humerus with a minimal bone resection and minimaldisruption of the metaphysis and diaphysis. Current designs utilize asemi-spherical articular dome with a small stem for rotationalstability. The under surface of the articular head is alsosemi-spherical and mates with the spherically machined humeral head.

The need for a shoulder replacement procedure may be created by thepresence of one of a number of conditions. One such condition is thedeterioration of the patient's rotator cuff. Specifically, an intactrotator cuff stabilizes the humeral head in the glenoid fossa of ascapula during abduction of the arm. While it is stabilized in such amanner abduction of the arm causes the humeral head to translate only ashort distance in the superior direction (e.g. a few millimeters),whereby a space is maintained between the humeral head and the acromion.However, for patients with rotator cuff arthropathy, significantlygreater humeral excursion is observed.

Referring to FIG. 2, a healthy long bone in the form of humerus 1 isshown. The humerus 1 includes a healthy humeral head 2.

Referring now to FIG. 3, a diseased humerus 3 is shown. The diseasedhumerus 3 includes a diseased or flattened humeral head 4. Whereas thehealthy humeral head 2 of the healthy humerus 1 of FIG. 2 has agenerally hemispherical shape, the flattened humeral head 4 is quiteflat and only slightly domed.

Referring now to FIGS. 4, 5 and 6, a prior art prosthesis 5 is shown.Referring first to FIG. 4, the prosthesis 5 is shown installed on thediseased humerus 3. The prosthesis 5 is positioned over flattened heador bony defect 4. The prosthesis 5 includes a hollow generallyhemispherical cup 6. Extending distally from the interior of the cup 6is a generally conically shaped stem 7 that anchors the prosthesis 5into the humerus 3.

Referring now to FIGS. 5 and 6, the prosthesis 5 is shown implanted in ashoulder joint. As shown in FIG. 5, the humerus 3 is shown in a positionin which the arm is resting against the patient's torso. Articulatingsurface of the cup 6 of the prosthesis 5 is shown in contact with thescapula 7, the clavicle 8, and the acromion 9. As can be seen in FIG. 5,in this downward position of the humerus 3 the prosthesis 5 provides thearticulating surface of cup 6 in contact with the acromion 9, theclavicle 8, and the scapula 7 to provide for a acceptable artificialjoint in this position.

However, referring to FIG. 6, the humerus 3 is shown abducted in thedirection of arrow 10 such that the long bone or humeral centerline 11is at an angle α of about fifteen (15) degrees with the verticalcenterline 12. As can be seen in FIG. 6, on a slight abduction offifteen degrees, the acromion 9 is positioned outside the articulatingsurface 6 of the prosthesis 5 causing the acromion 9 to impinge upon thehumerus 3 causing great pain to the patient and severely limited motionof the humerus 3.

In particular, hyper-translation of the humeral head in the superiordirection is observed in patients with massive rotator cuff deficiency,thereby resulting in articulation between the superior surface of thehumeral head and both the inferior surface of the acromion and theacromioclavicular joint during abduction of the patient's arm. Sucharticulation between these components accelerates humeral articulardestruction and the erosion of the acromion and acromioclavicular joint.Moreover, such bone-to-bone contact is extremely painful for thepatient, thereby significantly limiting the patient's range of motion.In short, patients with massive rotator cuff tear and associatedglenohumeral arthritis, as is seen in cuff tear arthropathy, mayexperience severe shoulder pain, as well as reduced function of theshoulder.

In order to treat patients suffering from cuff tear arthropathy, anumber of prostheses and techniques utilizing existing prostheses haveheretofore been designed. For example, surgeons heretofore utilized arelatively large humeral head prosthesis in an attempt to completelyfill the shoulder joint space. It was believed that such use of a largeprosthesis would increase the efficiency of the deltoid muscle, therebyimproving motion of the shoulder. However, clinical experience has shownthat such use of a large humeral head prosthesis (overstuffs) theshoulder joint thereby increasing soft tissue tension, reducing jointrange of motion, and increasing shoulder pain. Moreover, such use of anoversized prosthetic head fails to resurface the area of the greatertubercle of the humerus, thereby allowing for bone-to-bone contactbetween the greater tubercle and the acromion during abduction of thepatient's arm.

A number of humeral head bipolar prostheses have also been utilized inan attempt to address the problems associated with cuff teararthropathy. It was believed that the relatively unstrained motion ofthe bipolar head would improve shoulder motion. However, heretoforedesigned bipolar prosthetic heads include relatively large offsets,thereby overstuffing the shoulder joint in a similar manner as describedabove. Moreover, scar tissue may form around the bipolar head thereby(freezing) the dual articulating motion of the prosthesis that has beenknown to create a large hemi arthroplasty that likewise overstuffs theshoulder joint. In addition, such bipolar prosthetic heads do not coverthe articulating surface between the greater tubercle and the acromion,thereby creating painful bone-to-bone contact between them.

Yet further, a number of techniques have heretofore been designed inwhich the relatively rough surface of the greater tubercle is resurfacedwith an osteotome or high speed burr. Although this approach results ina smoother tubercle contact surface, relatively painful bone-to-bonearticulating contact still occurs, thereby reducing the patient's rangeof motion.

More recently, the assignee of the applicant of the present inventionhas invented a method and apparatus for performing a shoulderreplacement procedure in a treatment of a cuff tear arthroplasty whichhas been filed in the U.S. Patent and Trademark Office under U.S.application Ser. No. 09/767,473 filed Jan. 23, 2001, hereby incorporatedin its entirety by reference in this application. This applicationprovides for a method and apparatus for treating cuff tear arthroplastyutilizing a total shoulder replacement prosthesis. This prosthesisincludes an artificial head as well as a stem that extends into a rimmedmedullary canal. Such a prosthesis is limited to use with a totalshoulder prosthesis and is not suitable for use with bone sparingimplants for the initial treatment of the degenerative arthritis.

What is needed, therefore, is a method and apparatus for performing bonesparing arthroplasty shoulder replacement surgery utilizing bone sparingimplants for the initial treatment of degenerative arthritis, which willbe useful in the treatment of cuff tear arthroplasty, which overcomesone or more of the aforementioned drawbacks. What is particularly-neededis a method and apparatus for performing a bone sparing implant shoulderprocedure that eliminates painful articulation between the greatertubercle of the humerus and the acromion.

SUMMARY OF THE INVENTION

The present invention provides for an extended articulation resurfacingshoulder that provides a low-friction prosthetic bearing surface forarticulation between the greater tuberosity and the acromion. Such aprosthesis is utilized with a bone sparing minimal resection of aportion of the humeral head.

The present invention provides for an extended articulation resurfacingshoulder with superior/lateral flange for extended articulation into thecoracoacromial arch.

According to one embodiment of the present invention, a prosthesis foruse in performing joint arthroplasty is provided. The prosthesis is tobe fitted to a long bone. The prosthesis includes a first body having afirst body articulating surface defining a generally circular outerperiphery of the first body articulating surface. The first body has asupport surface opposed to first body articulating surface. The supportsurface is adapted to receive the head of the long bone. The prosthesisalso includes a second body operably associated with the first body. Thesecond body has a second body articulating surface extending from aportion of the circular outer periphery of the first body articulatingsurface.

According to another embodiment of the present invention, a tool kit forpreparing a humerus to receive a prosthesis is provided. The prosthesishas a first body having a first articulating surface and an opposedfirst support surface and has a second body having a second articulatingsurface and an opposed second support surface. The kit is used toprepare the humerus to receive the prosthesis. The tool kit includes areamer for preparing a first prepared surface on the humerus. The firstprepared surface receives the first support surface. The tool kit alsoincludes a bone cutting tool for preparing a second prepared surface onthe humerus. The second prepared surface receives the second supportsurface.

According to a further embodiment of the present invention, a method forperforming shoulder arthroplasty for an indication of rotator cuff teararthropathy is provided. The method includes the step of providing aprosthesis with a first body having a first articulating surface and anopposed first support surface and with a second body having a secondarticulating surface and an opposed second support surface. The methodalso includes the step of providing a tool kit for preparing a humerusfor receiving the prosthesis. The method includes the step of preparinga first prepared surface for cooperation with the first support surfacewith the tool kit. The method further includes the step of preparing asecond prepared surface for cooperation with the second support surfacewith the tool kit. The method also includes the step of implanting theprosthesis onto the first prepared surface and the second preparedsurface. The method also includes the step of providing an instrumentfor preparing a surface on a long bone, providing a plurality of trials,each of said trials being adapted to mate with the surface, selectingone of the plurality of trials, performing a trial reduction on said oneof said plurality of trials, determining if said one of said pluralityof trials is satisfactory, performing additional trial reductions asrequired, selecting one of a plurality of joint prostheses correspondingto one of said plurality of trials based upon the trial reductions, andimplanting the selected one prosthesis onto the long bone.

The technical advantage of the present invention includes the ability toprovide a low friction bearing surface between the greater tuberosityand the acromion. For example, according to one aspect of the presentinvention, a superior/lateral flange extends from a periphery of thehemispherical body of the prosthesis, which flange provides for extendedarticulation in the coracoacromial arch. Thus, the present inventionprovides a low friction bearing surface between the greater tuberosityand the acromion.

The technical advantages of the present invention further include theability to provide for an effective remedy for rotator cuff teararthropathy as part of a bone saving surgical procedure. For example,according to one aspect of the present invention, a prosthesis isprovided which includes a generally hollow hemispherical body whichmates with a slightly resected humeral head. Thus, the present inventionprovides for a surgical procedure with minimal bone loss.

According to another embodiment of the present invention, a cuttingguide for removal of bone during arthroplasty is provided. The cuttingguide includes a housing having a first portion and a second portion.The first portion includes an attachment mechanism adapted to couple thehousing to the bone during arthroplasty and the second portion includinga wall defining a continuous path. A blade for cutting the bone is alsoincluded, such that the blade slides along the arcuate recess, cuttingthe bone in a shape matching the continuous path.

According to yet another embodiment of the present invention, a methodfor removing bone during arthroplasty is provided. The method includesusing a cutting guide that has a first portion and a second portion. Thefirst portion includes an attachment mechanism adapted to couple thehousing to the bone during arthroplasty and the second portion includinga wall defining a continuous path. The first portion is attached onto abone. A blade is inserted into the continuous path and slid along thepath so as to remove bone in the shape of the path.

According to yet another embodiment of the present invention, a kit foruse in performing joint arthroplasty is provided. The kit includes aprosthesis to be fitted to a long bone. The prosthesis includes a firstbody having a first body articulating surface defining a generallycircular outer periphery thereof and having a support surface opposed tothe first body articulating surface adapted to receive the head of thelong bone. The prosthesis further includes a second body operablyassociated with the first body, the second body having a second bodyarticulating surface extending from a portion of the circular outerperiphery of the first body articulating surface. The kit also includesa cutting guide that includes a housing having an attachment mechanismadapted to couple the housing to the bone during arthroplasty and a walldefining a continuous path. The cutting guide also includes a blade forcutting the bone, the blade fitting within and sliding along thecontinuous path such that the blade cuts the bone in a shape matchingthe second body articulating surface.

Other technical advantages of the present invention will be readilyapparent to one skilled in the art from the following figures,descriptions and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure relates generally to prosthetic joints, and moreparticularly to a shoulder joint system that includes a metaphysealcomponent and an instrument preparing the bone to receive themetaphyseal component.

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in connection with the accompanying drawings, in which:

FIG. 1 is a plan view of a extended head humeral prosthesis according tothe present invention shown in position implanted on a diseased humerus;

FIG. 2 is a plan view of a healthy humerus;

FIG. 3 is a plan view of a diseased humerus;

FIG. 4 is a plan view of a prior art humeral prosthesis;

FIG. 5 is a plan view of a prior art humeral prosthesis shown inposition implanted on a diseased humerus with the humerus shown in theretracted position;

FIG. 6 is a plan view of a prior art humeral prosthesis shown inposition implanted on a diseased humerus with the humerus shown in theextended position with the humerus impinged on the distal acromion;

FIG. 7 is an enlarged plan view of the extended head humeral prosthesisof FIG. 1;

FIG. 8 is a plan view of the extended head humeral prosthesis of FIGS. 1and 7 shown in position implanted on a diseased humerus and incooperation with the glenoid cavity shown in the retracted position;

FIG. 9 is a plan view of the extended head humeral prosthesis of FIGS. 1and 7 shown in position implanted on a diseased humerus and incooperation with the glenoid cavity shown in the abducted position freefrom impingement in the glenoid cavity;

FIG. 10 is an enlarged plan view of the extended head humeral prosthesisof FIGS. 1 and 7;

FIG. 11 is a cross sectional view of the extended head humeralprosthesis of FIG. 10;

FIG. 12 is an auxiliary view of the extended head humeral prosthesis ofFIG. 10 along the lines 12-12 in the direction of the arrows;

FIG. 13 is a plan view of a reamer assembly to prepare a humeral headfor the extended head humeral prosthesis of FIGS. 1 and 7;

FIG. 14 is a plan view, partially in cross section of a cutting guidefor use with a cutter to prepare a humeral head for the extended headhumeral prosthesis of FIGS. 1 and 7;

FIG. 15 is a top view of the cutting guide of FIG. 14;

FIG. 16 is plan view of a tool kit for preparing a humeral head for theextended head humeral prosthesis of FIGS. 1 and 7;

FIG. 17 is plan view of an end mill for preparing a humeral head for theextended head humeral prosthesis of FIGS. 1 and 7;

FIG. 18 is a plan view of another cutting guide for use with a cutter toprepare a humeral head for the extended head humeral prosthesis of FIGS.1 and 7;

FIG. 19 is a top view of the cutting guide of FIG. 18;

FIG. 20 is plan view of another tool kit for preparing a humeral headfor the extended head humeral prosthesis of FIGS. 1 and 7;

FIG. 21 is a plan view of another embodiment of a extended head humeralprosthesis according to the present invention;

FIG. 22 is a cross sectional view of the extended head humeralprosthesis of FIG. 21;

FIG. 23 is an auxiliary view of the extended head humeral prosthesis ofFIG. 21 along the lines 23-23 in the direction of the arrows;

FIG. 24 is a plan view of a tool kit for preparing a humeral head forthe extended head humeral prosthesis of FIGS. 21-23;

FIG. 25 is a process flow chart for a method of performing shoulderarthroplasty surgery according to another embodiment of the presentinvention;

FIG. 26 is a plan view of a cutting guide according to one embodiment ofthe present invention;

FIG. 27 is a bottom view of the cutting guide of FIG. 26;

FIG. 28 is a plan view of the cutting guide of FIG. 26 on a humerus;

FIG. 29 is another plan view of the cutting guide of FIG. 26 on ahumerus; and

FIG. 30 is a process flow chart for a method of using the cutting guideof FIGS. 26-29.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention and the advantages thereof are bestunderstood by referring to the following descriptions and drawings,wherein like numerals are used for like and corresponding parts of thedrawings. Referring now to FIG. 7, an embodiment of the presentinvention is shown as prosthesis 20. The prosthesis 20 is used inperforming bone preserving joint arthroplasty. The prosthesis 20 is tobe fitted to the head of a long bone. For example, the long bone asshown in FIG. 7 is in the form of humerus 3. The prosthesis 20 includesa first body 22 having an articulating surface 24 defining a generallycircular outer periphery 26. The first body 22 also includes a secondsurface 28 opposed to the articulating surface 24. The second surface 28is adapted to receive the head of the humerus 3.

The prosthesis 20 further includes a second body 30 operably associatedwith the first body 22. The second body 30 has a second bodyarticulating surface 32 extending from a portion 34 of the circularperiphery 26 of the first articulating surface 24. The second bodyarticulating surface 32 is adapted to prevent impingement of theacromion 9 (see FIG. 1) with the humerus 3 when the humerus 3 is in theabducted position (see FIG. 8).

While the prosthesis of the present invention may be secured to thehumerus by securing of the second surface 28 to the humerus and bonyingrowth there between, preferably and as shown in FIG. 7, theprosthesis 20 further includes a stem 36 operably associated with thefirst body 22 or the second body 30. As shown in FIG. 7, the stem 36 isassociated with the first body 22. The stem 36 is adapted to assist insecuring the prosthesis 20 to the humerus 3. As shown in FIG. 7, theprosthesis 20 is an integral or one-piece item. It should be appreciatedthat the prosthesis 20 may be modular. For example, the stem 36 may be aseparate component from the first body 22 or the second body 30.Likewise, the second body 30 may be a separate component from the firstbody 22.

As shown in FIG. 7, the first body 22 may have any shape capable forarticulating motion with the glenoid cavity (see FIG. 8), however,preferably the articulating surface 24 is generally convex. For example,and as shown in FIG. 7, the articulating surface 24 may be generallyhemispherical. Likewise, the second surface 28 may likewise be generallyhemispherical with the first body 22 being generally a hollowhemisphere. Similarly, the second body articulating surface 32 ispreferably convex and may have a generally spherical shape. Likewise,the second body second surface 38 may likewise be generally spherical.The second body 30 may thus also be generally a sector of a hollowsphere.

To provide for smooth motion of the humerus 3 through the abduction ofthe humerus 3 with respect to glenoid cavity 14 (see FIG. 8) boundaryportion 40 of the prosthesis 20 located between the second articulatingsurface 32 and the first articulating surface 24 where the secondarticulating surface 32 extends from the first articulating surface 24is generally smooth and continuous.

Referring now to FIG. 1, the prosthesis 20 of the present invention isshown installed in the humerus 3 with the adjacent bones of the clavicle8, scapula 7 and acromion 9 shown in position. As shown in FIG. 1, thehumerus 3 is abducted into an angle β with respect to vertical erectbody reference line 42. As can be seen in FIG. 3, the acromion 9 extendspast the boundary portion 40 separating the first body 22 of theprosthesis 20 from the second body 30 of the prosthesis 20. Thus, thesecond body articulating surface 32 is utilized to prevent the acromion9 from impinging on the humerus 3.

Referring now to FIGS. 8 and 9, the humerus 3 is again shown in positionwith the adjacent skeletal structure. In FIG. 8, the long bone orhumerus 3 is shown in position when the upper arm is in position againstthe torso. At the humeral position as shown in FIG. 8, the angle βbetween the vertical centerline 42 and humeral centerline 44 isrepresented by an angle ββ of approximately 15 degrees. In this positionof the humerus 3, it can be seen that the acromion 9 is in contact withthe first articulating surface 24 at acromion distal edge or outer edge13. Referring now to FIG. 9, the humerus 3 is shown being abducted inthe direction of arrow 46 with the respective angle β equalingapproximately 60 degrees. In this abducted position, the outer edge 13of the acromion 9 is in a position such that the second articulatingsurface 32 of the second body 30 is used to provide a smootharticulating surface for the outer edge 13 of the acromion 9.

Referring now to FIG. 10, the prosthesis 20 is shown in greater detail.While the stem 36 of the prosthesis 20 may have any suitable shapecapable of providing support for the prosthesis 20 in the humerus 3,preferably, and as shown in FIG. 10, the stem 36 has a generalcylindrical shape. The first body 22 as shown in FIG. 10 may be in theform of a hollow hemisphere having a first longitudinal body centerline48. The stem 36 has a stem longitudinal centerline 50. As shown in FIG.10, the prosthesis 20 may be such that the first longitudinal bodycenterline 48 and the stem longitudinal centerline 50 are coincident.Such a configuration provides for a preferred central location of thestem 36.

Applicants have found that since the diseased humerus may becomeflattened around the humeral head, to provide adequate support to theprosthesis 20 in a diseased humerus, the support surface opposed to thearticulating surface 24 of the prosthesis 20 may include at least partof the second surface 28 to include a support surface 52 opposed to thefirst articulating surface 24. Preferably, for simplicity, the supportsurface may be generally planar.

To assist the prosthesis 20 in its strength and stability in the humerus3 and to promote the bony ingrowth around the prosthesis 20, theprosthesis 20 may include a porous coating 53 secured to, for example,the second surface 28 of the first body 22, the second surface 38 of thesecond body, the planar portion 52 of the second surface 28, as well ason the periphery of the stem 36. Any commercially available porouscoating will assist in the bony ingrowth of the prosthesis 20 to thehumerus 3. One particular porous coating is provided by the assignee ofthe instant application under the trade name POROCOAT®. Porous coatingmay be more fully understood by reference to U.S. Pat. No. 3,855,638 toPilliar, hereby incorporated in its entireties by reference. As shown inFIG. 10, the circular outer periphery 26 of the articulating surface 24of the first body 22 defines a first plane 54. Similarly, the secondarticulating surface 32 of the second body 30 defines a second surfaceperiphery 56. The second surface periphery 56 defines a second plane 58.The first plane 54 and the second plane 58 are non-coincident. The firstplane 54 and the second plane 58, therefore, define an angle αα therebetween. As shown in FIG. 10, the angle αα is obtuse. While the angle ααmay approach 180 degrees, the angle αα may likewise have a range ofabout 120 to 180 degrees. As shown in FIG. 20, the angle αα may bearound 138 degrees.

Referring now to FIGS. 11 and 12, the prosthesis 20 is shown in greaterdetail. As shown in FIG. 11, the stem 36 may be generally cylindricalhaving stem diameter SD and a length SL. The stem 36 may be tapered anddefined by an angle ω. The angle ω may be around 5 to 30 degrees.

The planar portion 52 of the prosthesis 20 may have any reasonablelocation with respect to the articulating surface 24 of the prosthesis20. The proper position of the planar portion 52 will depend on theflattening of the humeral head and how much corresponding amount ofresection may be required to the humeral head. The position of theplanar portion 52 with respect to the articulating surface 24 may bedefined by a flat dimension FD.

The hemispherical body 22 and second body 30 of the prosthesis 20 may bedefined with respect to a prosthetic center point 60. The articulatingsurface 24 may be defined by a radius R1 extending from center point 60the articulating surface 24. The second surface 28 may be defined by aradius R2 extending from the prosthetic center point 60 to the secondsurface 28. Similarly, the second articulating surface 32 may be definedby radius R4 from the prosthetic center point 60 to the secondarticulating surface 32. Similarly, the second surface of the secondbody 38 may be defined by radius R3 from the prosthetic center point 60to the second surface 28. For simplicity, the radii R1 and R4 may beidentical and for simplicity the radii R2 and R3 may be identical.

Referring now to FIG. 12, the underside of the prosthesis 20 is shown.

The prosthesis 20 may have any size compatible with the humerus.Preferably, and as shown in FIGS. 7 through 12, the prosthesis 20preferably blends with the periphery of the humerus. Thus, the size ofthe prosthesis 20 is governed generally by the size of the anatomicalhumerus.

The prosthesis 20 may be made of any suitable durable material that iscompatible with the human anatomy. For example, the prosthesis 20 may bemade of a ceramic, a plastic or a metal. If made of a metal, theprosthesis 20 may be made, for example, of a cobalt chromium alloy, atitanium alloy, or a stainless steel alloy.

Referring now to FIG. 16, an instrument in the form of, for example, areamer assembly 62 is shown for use in reaming, for example, thearticulating surface 24 of the prosthesis 20 of FIG. 7.

As shown in FIG. 13, the reamer assembly 62 includes a tool driver 64.The tool driver 64 includes a body 66 having a cutting tool adapter 68and a drive adapter 70. The reamer assembly 62 also includes a reamer72. The reamer 72 is connected to the tool driver 64 by the cutting tooladapter 68. The reamer 72 may be a hemispherical grater type reamer.

Referring now to FIGS. 14 and 15, a bone cutting tool guide 74 is shown.The tool guide 74 may include a body 76 having a cylindrical bore 78 forreceiving a guide pin 80 and a elongated slot 82 for receiving a cuttingtool in the form of osteotome 84. The tool guide 74 is used to preparesurface 88 of humerus 3.

Referring now to FIG. 16, a tool kit 86 is shown for preparing a humerusto receive a prosthesis, for example, prosthesis 20 of FIGS. 7 through12.

As shown in FIGS. 7 through 12, the prosthesis 20 includes the firstbody 22 having the first articulating surface 24 and an opposed firstsurface support surface 28. The prosthesis 20 also includes the secondbody 30 that has the second articulating surface 32 and an opposedsecond support surface 38.

Referring again to FIG. 16, the kit 86 is used for preparing the firstsupport surface 28 and the second support surface 38. The tool kit 86 ofFIG. 16 includes the reamer 72 and may include the tool driver 64 toform the reamer assembly 62. The tool kit 86 further includes a bonecutting tool 84 for preparing a second prepared surface on the humerus 3for receiving the second support surface 38 of, for example, theprosthesis 20.

As shown in FIG. 15, the bone cutting tool 84 is used to prepare secondprepared surface 88 on the humerus 3. As shown in FIG. 15, the secondprepared surface 88 represents the inside surface of a cylinder. Such ashape on the humerus is necessary to accommodate the inner edge 90 ofthe second body 30 of the prosthesis 20. (See FIG. 11).

Preferably and as shown in FIG. 16, the kit 86 further includes the bonecutting tool guide 74 for guiding the osteotome 84 through the elongatedslot 82 of the bone cutting tool guide 74. The osteotome 84 may bestruck with mallet 96.

Referring now to FIG. 10, it should be appreciated that if the angle ααapproaches 180 degrees, it may be possible to provide for the reaming ofthe humerus with a reamer assembly 62 (see FIG. 13) and merely pivot thereamer assembly 62 to form a contour for both the second surfaces 28 and38.

It should be appreciated, however, as the angle αα moves from 180degrees to something less, for example, 140 degrees the inner edge 90 ofsecond body 30 of prosthesis 20 (see FIG. 11) moves closer to the stemcenterline 50 such that a generally hemispherical grater-type reamersuch as that of FIG. 13 may not be appropriate to prepare thehemispherical head of the humerus. Therefore, the guide 74 of the kit 86provides for a surface 88 that is generally cylindrical to permit thecorner 90 of the prosthesis 20 to be fully seated into the humerus.

It should be appreciated that the bone cutting tool necessary to preparethe humerus may include a drill, a reamer, a broach, a saw or anosteotome.

Referring now to FIGS. 17 through 20, an alternate tool kit 186 forpreparing a humerus is shown. Referring first to FIG. 17, end mill 192is shown. End mill 192 may be any commercially available milling cuttercapable of end cutting.

Referring now to FIGS. 18 and 19, a bone cutting tool guide 174 is shownfor use with the end mill 192 of FIG. 17. The guide 174 includes a body176. The body 176 includes an opening 178 for cooperation with locationpin 180. The location pin 180 is used to orient the guide 174 withrespect to the humerus 3. The guide 174 further defines a plurality ofslots 182 formed in the body 176.

Referring to FIG. 19, the slots 182 extend an angle θθ about theperiphery of concave inner surface 194 of the guide 174. The slots 182are aligned somewhat parallel to each other and slightly spaced apart.The slots 182 are close enough to minimize the amount of material notcovered by the slots but far enough apart to provide enough strength tothe guide 174, particularly around the slots 182.

Referring now to FIG. 20, the kit 186 is shown. The kit 186 includesreamer assembly 162 for preparing the first prepared surface on thehumerus. The reamer assembly 162 is similar to reamer assembly 62 ofFIG. 13 and includes a tool driver 164 similar to the tool driver 64 ofFIG. 13 as well as a grater type hemispherical reamer 172 similar to thereamer 72 of the reamer assembly 62 of FIG. 13. The kit 186 furtherincludes end mill 192 as well as an osteotome 184 similar to osteotome84 of the kit 86 of FIG. 16. The osteotome 184 serves to remove thematerial remaining after the end mill 192 removes materials in alignmentwith the slots 182 of the guide 174. Preferably and as shown in FIG. 20,the kit 186 may further include the guide 174. Further, the kit 186 mayinclude a surgical mallet 196. The surgical mallet 196 is used to strikethe osteotome 184.

Referring now to FIGS. 21, 22 and 23, an alternate embodiment of thepresent invention is shown as prosthesis 120. Prosthesis 120 is similarto prosthesis 20 of FIGS. 7 through 12 except that prosthesis 120 isdesigned to take into consideration the limit in installing theprosthesis onto the prepared humeral head. Mainly, the prosthesis 120takes into consideration the inability to clear the edge 90 of theprosthesis 20 when utilizing a spherically shaped humeral head.

Referring now to FIG. 21, the prosthesis 120 includes a first body 122having a hemispherical articulating surface 124 and an opposed concavearcuate surface 128. The first body 122 also has a planar portion 152opposing the articulating surface 124. The prosthesis 120 furtherincludes a tapered cylindrical stem 136 extending inwardly from theplanar portion 152 of the first body 122. The prosthesis 120 furtherincludes a second body 130 extending from circular outer periphery 126of the first body 122. A boundary portion 140 is located between thefirst body 122 and the second body 130 and is preferably smooth andcontinuous. Unlike the prosthesis 20, the second body 130 of theprosthesis 120 has an opposed surface in the form of a cylindrical innerperiphery 138. The cylindrical periphery 138 is designed to matingly fitwith the cylindrical surface prepared on the humeral head.

Referring now to FIG. 22, the cylindrical periphery 138 is shown ingreater detail. The cylindrical periphery 138 is defined by a radiusR.sub.c extending from stem centerline 150.

Referring now to FIG. 23, another view of the cylindrical periphery 135of the prosthesis 120 is shown. The cylindrical periphery 135 is againdefined by a radius R.sub.c from stem centerline 150.

Referring now to FIG. 24, an alternate tool kit is shown as tool kit286. The tool kit 286 is used to prepare a humerus for the prosthesis ofthe present invention. The tool kit 286 includes a reamer assembly 262similar to the reamer assembly 162 of the kit 186 of FIG. 20. The toolkit 286 further includes a cylindrical end cutting reamer 292 having acylindrical cutting surface 297 and a guiding surface 298. The kit 286further includes a guide 274 for guiding the cylindrical reamer 292 in aproper path to properly prepare the humerus. The guide 274 includes abody 276 defining an opening 278 for cooperation with location pin 280,which is utilized to properly position the guide 274 on the humerus. Thebody 276 of the guide 274 further includes an arcuate elongated slot 282that cooperates with the guiding surface 298 of the reamer 292 to guidethe reamer along a proper path. The arcuate slot 282 is defined by anincluded angle θθθ.

Referring now FIG. 25, an alternate embodiment of the present inventionis shown as surgical method 300. The method 300 includes the first step302 of providing a prosthesis with a first body having a firstarticulating surface and an opposed first support surface and with asecond body having a second articulating surface and an opposed secondsupport surface. The method 300 further includes a second step 304providing a tool kit for preparing a humerus for receiving theprosthesis. The method 300 further includes a third step 306 ofpreparing a first prepared surface for cooperation with the firstsupport surface with the tool kit. The method 300 also includes a fourthstep 308 of preparing a second prepared surface for cooperation with thesecond support surface with the tool kit. The method 300 furtherincludes a fifth step 310 of implanting the prosthesis onto the firstprepared surface and the second prepared surface.

Turning now to FIG. 26, another embodiment of a cutting guide 400 forpreparing a second prepared surface on the humerus 3 for receiving thesecond support surface 38 of the prosthesis 20 is illustrated. Thecutting guide 400 includes a housing 401 having first portion 402 and asecond portion 404. The first portion 402 includes a positioningmechanism 408 for positioning the cutting guide 400 on the humerus 3 (asshown in FIG. 28). In this embodiment, the positioning mechanism 408 isan aperture for receiving a guide pin 430 (shown in FIG. 28). The firstportion also includes an attachment mechanism 409 for attaching thecutting guide 400 to the humerus 3. In this embodiment, the attachmentmechanism 409 is in the form of two apertures on either side of thefirst portion 402. Pins 431 (FIG. 29) are placed through the aperturesand pin the cutting guide 400 to the humerus 3. In some embodiments,more or less pins 431 and apertures 409 may be used. Alternatively,other known methods for attaching the cutting guide 400 to the humerus 3may be used.

The second portion 404 includes a wall 406 that defines a continuouspath 410. In the embodiment illustrated, the continuous path is acontinuous arcuate (or parabolic) recess 410. However, in otherembodiments, the continuous path may be just a cut-out in the wall.Also, the path need not be arcuate, it may be any shape to match thesecond body 30 of the prosthesis 20 (FIG. 11). In other words, the pathmay be a single straight line, a v-shape, a triangular shape, or othershape. The arcuate recess 410 receives a blade 412 (FIG. 28). The blade412 is slidingly moveable along the arcuate recess 410 so as to removebone from the humerus 3. The humerus 3 as shown in FIG. 28 isillustrated with a resected portion 414. The shape of the resectedportion 414 is to accommodate the inner edge 90 of the second body 30 ofthe prosthesis 20 (FIG. 11).

Returning now to FIG. 26, the first portion 402 includes a first end 416and a second end 418. The first end 416 of the first portion 402 isconnected to a first end 420 of the second portion 404 and the secondend 418 of the first portion 402 is connected to a second end 422 of thesecond portion 404. In the illustrated embodiment, the cutting guide 400is a single molded piece. However, in some embodiments, the cuttingguide 400 may be modular, such that the first and second portions 402,404 are separate pieces that are locked together at the first and secondends 416, 418, 420, 422.

As shown in FIG. 26, the wall 406 includes an outer periphery 424 thatextends outwardly from the first portion 402. In the illustratedembodiment, the arcuate recess 410 is furthest away from the firstportion at its centermost point 426. The wall 406 of the second portion404 also has a varying height. In one embodiment, the heights graduallydecreases from the first end 420 to the centermost point 426 and thengradually increases until the second end 422. Thus, the arcuate recessis arcuate (or parabolic) both in a vertical and in a horizontaldirection.

Turning now to FIG. 27, a bottom view of the cutting guide 400 is shown.The arcuate recess 410 is clearly shown to be a continuous path in thehorizontal direction. Turning now to FIG. 28, the cutting guide 400 isshown on the humerus 3. As shown, the housing 401 is attached to thehumerus via single pin 430. The blade 412 is inserted into the arcuaterecess 410. In this embodiment, the blade 412 includes cutting teeth 432for resecting the humerus 3. The blade 412 also includes a depth marker434. The blade 412 is used by sliding it along the arcuate recess 410and also vertically. The depth marker 434 allows the user to know whento not insert the blade 412 further down into the housing 401. The depthmarker 434 may be a visual mark, such as the line shown. The depthmarker 434 may also be a plurality of marks, with each markcorresponding to a different depth. In other embodiments, the depthmarker 434 may be a physical protrusion that will act as a stopper andnot allow the blade 412 to be inserted any further into the recess 410.

Both the first and second bodies 402, 404 may also include markers 435to be used to align the cutting guide 400 with the greater tubercle. Asshown, the markers 435 are vertical lines, but they may also be raisedportions or other types of visual indicators. This allows the user tomore easily ensure that the cutting guide 400 is in the proper locationrelative to the humerus 3.

In some embodiments, it may be desirable to provide a plurality ofprostheses 20 (FIG. 11). The plurality of prostheses 20 could havesecond support surfaces 38 that vary in size. In such embodiments, aninstrument kit providing a plurality of cutting guides 400 may beprovided, with each cutting guide 400 having an arcuate recess 410 of adifferent shape. Alternatively, only a single cutting guide 400 may beprovided, but a plurality of blades 412 may be provided, each with adifferent depth marker 434.

In one embodiment, guide and blade will be made from stainless steel. Itis also contemplated that other sterilizable materials may also be used.In some embodiments, the guide and blade may be made of plastic orceramic.

Turning now to FIG. 30, a method according to one embodiment of thepresent invention will be described. First, a portion of the head isreamed at step s450. After the head is prepared by the reamer (notshown), at step s452, the cutting guide 400 is slid over the guide pin430 onto the humerus 3. In some embodiments, the cutting guide 400 maybe positioned onto the humerus 3 using other known methods. Next, atstep s454, the first portion 402 of the cutting guide 400 is attachedonto the humerus 3. This may be done by inserting the pin 430 into theaperture 428. In other embodiments, other attachment mechanisms may beused. The blade 412 is then inserted into the arcuate recess 410 (steps456) and slid up and down and also along the arcuate recess 410 toremove the bone (step s458). In some embodiments, the blade 412 includesthe depth marker 434 and as the blade is moved vertically, the user onlymoves it downward as far as the depth marker 434.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions, andalterations can be made therein without departing from the spirit andscope of the present invention as defined by the appended claims.

What is claimed is:
 1. A kit for use in performing joint arthroplasty,the kit comprising: a prosthesis to be fitted to a long bone, theprosthesis including a first body having a first body articulatingsurface defining a generally circular outer periphery thereof and havinga support surface opposed to the first body articulating surface adaptedto receive the head of the long bone, and a second body operablyassociated with the first body, the second body having a second bodyarticulating surface extending from a portion of the circular outerperiphery of the first body articulating surface; and a cutting guide,the cutting guide including a housing having an attachment mechanismadapted to couple the housing to the bone during arthroplasty and a walldefining a continuous path; a blade for cutting the bone, the bladefitting within and sliding along the continuous path such that the bladecuts the bone in a shape matching the second body articulating surface.2. The kit according to claim 1, wherein the cutting guide includes afirst and second portion, the second portion having the wall definingthe continuous path.
 3. The kit according to claim 1, wherein thecontinuous path is a continuous arcuate recess.
 4. The kit according toclaim 3, wherein the continuous, arcuate recess is arcuate in both ahorizontal and a vertical plane.
 5. The kit according to claim 1,further comprising a reamer for reaming the head and preparing thehumerus to receive the first body.